Chitosan-based ion-imprinted cryo-composites with excellent selectivity for copper ions.

An original strategy is proposed here to design chitosan-based ion-imprinted cryo-composites (II-CCs) with pre-organized recognition sites and tailored porous structure by combining ion-imprinting and ice-templating techniques. The cryo-composites showed a tube-like porous morphology with interconnected parallel micro-channels, the distance between the channel walls being around 15 μm. Both the entrapment of a natural zeolite and the presence of carboxylate groups, generated by partial hydrolysis of amide moieties, led to II-CCs with controlled swelling ratios (25-40 g/g, depending on pH) and enhanced overall chelating efficiency (260 mg Cu ²⁺ /g composite). To point out the importance of introducing Cu ²⁺ recognition sites, sorption experiments using mixtures of Cu ²⁺ and other competing ions (Co ²⁺ , Ni ²⁺ , Zn ²⁺ or/and Pb ²⁺ ) were also carried out. The higher values of selectivity coefficients obtained for the II-CCs compared to those of non-imprinted ones highlight the remarkable potential of our sorbents for decontamination of wastewaters and recycling of Cu ²⁺ ions.
(Copyright © 2018 Elsevier Ltd. All rights reserved.)